I'm building up an old French bike that I got as a bare frame. Grand Bois and René Herses sure would be nice, but they'd also outvalue the rest of the bike 😃
I had first considered Michelin World Tour tires in 650-44B. Apparently they haven't changed much in the last 50 or so years, yet I've been hearing they are not particularly good these days (if they ever were...)
Michelin World Tour / "Retro Classic Access Line(?)"
Hutchinson,
a brand with a bad reputation but an upward trajectory according to Sheldon, also make a classic 42 mm tire simply named Urban. It seems to be less widely stocked.
Hutchinson Urban
Ralson, an unfamiliar name to me that I recently learned has a formidable 60 % or so market share in India, also makes a similar looking heritage tire in Nylon compound 😃
Ralson ? Model
I've also considered some of the slightly more performance-oriented gravel tires. With gumwalls, they wouldn't perhaps look too out of place. One such is the WTB Byway.
WTB Byway
I had a pair of WTB Horizon slicks that I regretfully sold because they wouldn't fit the bike I had then. I have GK semislicks in 38 mm width but they seem to easily lose traction on loose gravel. That's why I'm looking for tires with a more pronounced tread.
I've also struggled with mounting the said Gravelkings and WTB Horizons on my single-wall Schurmann rims so that they sit evenly, but this might be due to using slightly undersize inner tubes (35 mm nominal in 38 mm tire). Heavy lugged winter tires didn't have this issue (as much). I'll have to try again once I come across some 40 mm 650B inner tubes. Some people suggest 26"/559 inner tubes should also work fine 🤔